The present invention relates to inline skate wheels, and more particularly to inline skate wheels having an internal tire support structure allowing a softer tire material without increased roll resistance.
Inline skates have been in wide use since the early 1990's. Inline skates generally comprise a boot, shoe, or the like, having a multiplicity of wheels attached to the bottom, which wheels are in-line. Early skate wheels comprised a relatively hard injection molded polyurethane plastic inner core and a relatively soft open cast thermoset polyurethane tire surrounding the inner core. Individual wheels may vary in outside diameter and in relative softness of the tire. A softer tire results in greater grip, and a harder tire reduces rolling resistance.
The inner core in skate wheels designed in the early 90's generally comprised a hard plastic material and a diameter about sixty to seventy percent of the tire outside diameter. A smaller diameter inner core may result in a wheel without sufficient support under horizontal traction loading (i.e., side loads). A larger diameter inner core may result in a “hard” feel and vibrations. Typically, the tire may be a 76 A hardness (76 Shore Hardness A), material. A harder tire material may be used to obtain greater support, but with a loss of traction, and a softer material may be used to obtain greater traction, but with a loss of support. Such typical tire may be made from Polytetramethylene Ether Glycol (PTMEG) ether-based, high rebound, thermoset, polyurethane elastomer formulation using a gravity fill, liquid to solid, cured casting manufacturing method.
U.S. Pat. No. 5,908,519 issued Jun. 1, 1999 for “Hollow Core In-line Skate Wheel Having Contour Conforming Polyurethane Wall,” teaches skate wheels having a tubular bladder. The bladder allows the tire to conform to a surface for greater traction. Unfortunately, when used by roller hockey players weighing one hundred and seventy five pounds or more, deformation of the tire (e.g., conformance of the tire to the riding surface) allowed by the bladder resulted in increased roll resistance. U.S. Pat. No. 5,922,151 issued on Jul. 13, 1999 for “Polyurethane Skate Wheel with Shaped Foam Core,” utilizes a foam insert suspended in the tire to replace the bladder of the '519 patent, to reduce the conformance of the tire under straight rolling. The wheel of the '151 patent had slightly less roll resistance than the wheel of the '519 patent, but the energy absorption of the foam was inefficient, and heat build-up resulted.
In 1999, Kyrptonics in Cypress, Calif. introduced a skate wheel having an 82 A hardness solid insert bonded directly to the inner core. The insert is made of high rebound thermoset polyurethane with much lower compressive losses than the foam of the '151 patent, but the overall stiffness limits traction to be less than desirable. The Kyrptomics wheels reduce roll resistance, but do not provide sufficient structural support to allow a softer polyurethane material to be used for the tire. Redstar Wheels in Garden Grove, Calif. designed a skate wheel similar to the Kyrptonics wheels, but with a near 88 A hardness insert. The resulting wheel had low roll resistance, but at the cost of much reduced traction as well.
Another attempt at a low roll resistance skate wheel with good traction was made by Labeda Precision Sports, Inc. in Lake Elsinore, Calif. The Labeda wheels included an 85 A hardness transition layer bonded to the inner core, and a 78 A hardness rebound ring bonded to the transition layer. Although some improvements to performance were made, the Labeda wheel still required about a 76 A tire to avoid increased roll resistance.
The “Rink Rat” wheel manufactured by MPC in Cranston, R.I., have a soft inner layer covered by a harder outer layer, and is described in U.S. Pat. No. 6,036,278 issued Mar. 14, 2000 for “Multi Durometer Wheel for In-Line Skates,” and U.S. Pat. No. 6,227,622 issued May 8, 2001 for “Multilayer Skate Wheel.” Unfortunately, the soft inner core allows the Rink Rat wheels to deform (i.e., flatten) during straight line skating, resulting in roll resistance, and requires a tire of 76 A or greater hardness.
Roller hockey presently competes for audience with ice hockey. In order to be successful, roller hockey must provide the same “quickness” that ice hockey audiences are accustomed to. Obtaining such quickness requires skate wheels which overcome the deficiencies of known skate wheels, and unfortunately, the various wheels described above have failed to provide a wheel combining low rolling resistance for speed, and traction for maneuvering, and in general require a hard tire (i.e., at least 76 A hardness.) Thus, there remains a need for a skate wheel with reduced roll resistance and sufficient traction, and which does not result in heat buildup.